I created a WP plugin a little while back called “Facebook Events”. Basicly it allows you to post up an event (or multiple) on your WordPress site and then it automatically creates a new event on Facebook without ever having to leave WordPress.

Also, when users click to say they are attending either on the Blog or on Facebook, your blog post event will auto-update and show that person’s avatar if they are attending.

While it’s not really blackhat, I’m sure you guy’s could get creative with it.